Received: 25 August 2018
Accepted: 16 April 2019
First Online: 2 May 2019
Ethics approval and consent to participate
: The Institutional Review Board (IRB) of the University of Tsukuba Affiliated Hospital approved the present study (H27-085) and written informed consent was obtained from patients prior to surgery.
: Not applicable.
: The authors declare that they have no competing interests.
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